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            <h1>Node.js v0.8.12 Manual &amp; Documentation</h1>
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            <h2>Table of Contents</h2>
            <ul>
<li><a href="#dns_dns">DNS</a><ul>
<li><a href="#dns_dns_lookup_domain_family_callback">dns.lookup(domain, [family], callback)</a></li>
<li><a href="#dns_dns_resolve_domain_rrtype_callback">dns.resolve(domain, [rrtype], callback)</a></li>
<li><a href="#dns_dns_resolve4_domain_callback">dns.resolve4(domain, callback)</a></li>
<li><a href="#dns_dns_resolve6_domain_callback">dns.resolve6(domain, callback)</a></li>
<li><a href="#dns_dns_resolvemx_domain_callback">dns.resolveMx(domain, callback)</a></li>
<li><a href="#dns_dns_resolvetxt_domain_callback">dns.resolveTxt(domain, callback)</a></li>
<li><a href="#dns_dns_resolvesrv_domain_callback">dns.resolveSrv(domain, callback)</a></li>
<li><a href="#dns_dns_resolvens_domain_callback">dns.resolveNs(domain, callback)</a></li>
<li><a href="#dns_dns_resolvecname_domain_callback">dns.resolveCname(domain, callback)</a></li>
<li><a href="#dns_dns_reverse_ip_callback">dns.reverse(ip, callback)</a></li>
<li><a href="#dns_error_codes">Error codes</a></li>
</ul>
</li>
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          <div id="apicontent">
            <h1>DNS<span><a class="mark" href="#dns_dns" id="dns_dns">#</a></span></h1>
<pre><code>Stability: 3 - Stable</code></pre>
<p>Use <code>require(&#39;dns&#39;)</code> to access this module. All methods in the dns module
use C-Ares except for <code>dns.lookup</code> which uses <code>getaddrinfo(3)</code> in a thread
pool. C-Ares is much faster than <code>getaddrinfo</code> but the system resolver is
more constant with how other programs operate. When a user does
<code>net.connect(80, &#39;google.com&#39;)</code> or <code>http.get({ host: &#39;google.com&#39; })</code> the
<code>dns.lookup</code> method is used. Users who need to do a large number of look ups
quickly should use the methods that go through C-Ares.

</p>
<p>Here is an example which resolves <code>&#39;www.google.com&#39;</code> then reverse
resolves the IP addresses which are returned.

</p>
<pre><code>var dns = require(&#39;dns&#39;);

dns.resolve4(&#39;www.google.com&#39;, function (err, addresses) {
  if (err) throw err;

  console.log(&#39;addresses: &#39; + JSON.stringify(addresses));

  addresses.forEach(function (a) {
    dns.reverse(a, function (err, domains) {
      if (err) {
        throw err;
      }

      console.log(&#39;reverse for &#39; + a + &#39;: &#39; + JSON.stringify(domains));
    });
  });
});</code></pre>
<h2>dns.lookup(domain, [family], callback)<span><a class="mark" href="#dns_dns_lookup_domain_family_callback" id="dns_dns_lookup_domain_family_callback">#</a></span></h2>
<p>Resolves a domain (e.g. <code>&#39;google.com&#39;</code>) into the first found A (IPv4) or
AAAA (IPv6) record.
The <code>family</code> can be the integer <code>4</code> or <code>6</code>. Defaults to <code>null</code> that indicates
both Ip v4 and v6 address family.

</p>
<p>The callback has arguments <code>(err, address, family)</code>.  The <code>address</code> argument
is a string representation of a IP v4 or v6 address. The <code>family</code> argument
is either the integer 4 or 6 and denotes the family of <code>address</code> (not
necessarily the value initially passed to <code>lookup</code>).

</p>
<p>On error, <code>err</code> is an <code>Error</code> object, where <code>err.code</code> is the error code.
Keep in mind that <code>err.code</code> will be set to <code>&#39;ENOENT&#39;</code> not only when
the domain does not exist but also when the lookup fails in other ways
such as no available file descriptors.


</p>
<h2>dns.resolve(domain, [rrtype], callback)<span><a class="mark" href="#dns_dns_resolve_domain_rrtype_callback" id="dns_dns_resolve_domain_rrtype_callback">#</a></span></h2>
<p>Resolves a domain (e.g. <code>&#39;google.com&#39;</code>) into an array of the record types
specified by rrtype. Valid rrtypes are <code>&#39;A&#39;</code> (IPV4 addresses, default),
<code>&#39;AAAA&#39;</code> (IPV6 addresses), <code>&#39;MX&#39;</code> (mail exchange records), <code>&#39;TXT&#39;</code> (text
records), <code>&#39;SRV&#39;</code> (SRV records), <code>&#39;PTR&#39;</code> (used for reverse IP lookups),
<code>&#39;NS&#39;</code> (name server records) and <code>&#39;CNAME&#39;</code> (canonical name records).

</p>
<p>The callback has arguments <code>(err, addresses)</code>.  The type of each item
in <code>addresses</code> is determined by the record type, and described in the
documentation for the corresponding lookup methods below.

</p>
<p>On error, <code>err</code> is an <code>Error</code> object, where <code>err.code</code> is
one of the error codes listed below.


</p>
<h2>dns.resolve4(domain, callback)<span><a class="mark" href="#dns_dns_resolve4_domain_callback" id="dns_dns_resolve4_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for IPv4 queries (<code>A</code> records).
<code>addresses</code> is an array of IPv4 addresses (e.g.
<code>[&#39;74.125.79.104&#39;, &#39;74.125.79.105&#39;, &#39;74.125.79.106&#39;]</code>).

</p>
<h2>dns.resolve6(domain, callback)<span><a class="mark" href="#dns_dns_resolve6_domain_callback" id="dns_dns_resolve6_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve4()</code> except for IPv6 queries (an <code>AAAA</code> query).


</p>
<h2>dns.resolveMx(domain, callback)<span><a class="mark" href="#dns_dns_resolvemx_domain_callback" id="dns_dns_resolvemx_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for mail exchange queries (<code>MX</code> records).

</p>
<p><code>addresses</code> is an array of MX records, each with a priority and an exchange
attribute (e.g. <code>[{&#39;priority&#39;: 10, &#39;exchange&#39;: &#39;mx.example.com&#39;},...]</code>).

</p>
<h2>dns.resolveTxt(domain, callback)<span><a class="mark" href="#dns_dns_resolvetxt_domain_callback" id="dns_dns_resolvetxt_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for text queries (<code>TXT</code> records).
<code>addresses</code> is an array of the text records available for <code>domain</code> (e.g.,
<code>[&#39;v=spf1 ip4:0.0.0.0 ~all&#39;]</code>).

</p>
<h2>dns.resolveSrv(domain, callback)<span><a class="mark" href="#dns_dns_resolvesrv_domain_callback" id="dns_dns_resolvesrv_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for service records (<code>SRV</code> records).
<code>addresses</code> is an array of the SRV records available for <code>domain</code>. Properties
of SRV records are priority, weight, port, and name (e.g.,
<code>[{&#39;priority&#39;: 10, {&#39;weight&#39;: 5, &#39;port&#39;: 21223, &#39;name&#39;: &#39;service.example.com&#39;}, ...]</code>).

</p>
<h2>dns.resolveNs(domain, callback)<span><a class="mark" href="#dns_dns_resolvens_domain_callback" id="dns_dns_resolvens_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for name server records (<code>NS</code> records).
<code>addresses</code> is an array of the name server records available for <code>domain</code>
(e.g., <code>[&#39;ns1.example.com&#39;, &#39;ns2.example.com&#39;]</code>).

</p>
<h2>dns.resolveCname(domain, callback)<span><a class="mark" href="#dns_dns_resolvecname_domain_callback" id="dns_dns_resolvecname_domain_callback">#</a></span></h2>
<p>The same as <code>dns.resolve()</code>, but only for canonical name records (<code>CNAME</code>
records). <code>addresses</code> is an array of the canonical name records available for
<code>domain</code> (e.g., <code>[&#39;bar.example.com&#39;]</code>).

</p>
<h2>dns.reverse(ip, callback)<span><a class="mark" href="#dns_dns_reverse_ip_callback" id="dns_dns_reverse_ip_callback">#</a></span></h2>
<p>Reverse resolves an ip address to an array of domain names.

</p>
<p>The callback has arguments <code>(err, domains)</code>.

</p>
<p>On error, <code>err</code> is an <code>Error</code> object, where <code>err.code</code> is
one of the error codes listed below.

</p>
<h2>Error codes<span><a class="mark" href="#dns_error_codes" id="dns_error_codes">#</a></span></h2>
<p>Each DNS query can return one of the following error codes:

</p>
<ul>
<li><code>dns.NODATA</code>: DNS server returned answer with no data.</li>
<li><code>dns.FORMERR</code>: DNS server claims query was misformatted.</li>
<li><code>dns.SERVFAIL</code>: DNS server returned general failure.</li>
<li><code>dns.NOTFOUND</code>: Domain name not found.</li>
<li><code>dns.NOTIMP</code>: DNS server does not implement requested operation.</li>
<li><code>dns.REFUSED</code>: DNS server refused query.</li>
<li><code>dns.BADQUERY</code>: Misformatted DNS query.</li>
<li><code>dns.BADNAME</code>: Misformatted domain name.</li>
<li><code>dns.BADFAMILY</code>: Unsupported address family.</li>
<li><code>dns.BADRESP</code>: Misformatted DNS reply.</li>
<li><code>dns.CONNREFUSED</code>: Could not contact DNS servers.</li>
<li><code>dns.TIMEOUT</code>: Timeout while contacting DNS servers.</li>
<li><code>dns.EOF</code>: End of file.</li>
<li><code>dns.FILE</code>: Error reading file.</li>
<li><code>dns.NOMEM</code>: Out of memory.</li>
<li><code>dns.DESTRUCTION</code>: Channel is being destroyed.</li>
<li><code>dns.BADSTR</code>: Misformatted string.</li>
<li><code>dns.BADFLAGS</code>: Illegal flags specified.</li>
<li><code>dns.NONAME</code>: Given hostname is not numeric.</li>
<li><code>dns.BADHINTS</code>: Illegal hints flags specified.</li>
<li><code>dns.NOTINITIALIZED</code>: c-ares library initialization not yet performed.</li>
<li><code>dns.LOADIPHLPAPI</code>: Error loading iphlpapi.dll.</li>
<li><code>dns.ADDRGETNETWORKPARAMS</code>: Could not find GetNetworkParams function.</li>
<li><code>dns.CANCELLED</code>: DNS query cancelled.</li>
</ul>

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